Autoclaved aerated concrete: Experimental evaluation of its thermal properties at high temperatures

This paper presents the results of experimental measurements of thermal conductivity and of volumetric specific heat, ρ Cp, carried out at high temperature on autoclaved aerated concrete (AAC) specimens at different densities. The Knowledge of the correlation of thermal conductivity and specific heat with temperature is of fundamental importance in the study of the mechanical behaviour of building materials in presence of ire. The numerical verifications of ire resistance of structures are often carried out using computer codes that solve differential equations of thermal exchanges. For this reason a proper Knowledge of the above thermal properties as a function of temperature is required. The measurement of thermal conductivity and thermal diffusivity has been carried out using a Hot Disk Thermal Constants Analyser equipment. The experimental environment suitable to achieve high temperatures consists of a special controlled temperature oven in which measurements are made with sensors enclosed in two layers of refractory material (mica) suitable for working with acceptable accuracy in a range of temperatures between 500-1000 K. The results are also compared with the directions on the material provided by national and international standards but we realized that the thermal conductivity values at high temperatures, suggested by the standard EN 12602, are significantly lower than those experimentally measured in this study and thus they are not precautionary checks for computational ire resistance. We propose to investigate on the source of the suggested data and ask a revision of the above mentioned standard.